This invention relates generally to the art of electron beam discharge devices, including high energy charged particle accelerators, and more particularly concerns a particular anode structure useful in such devices.
In an electron beam discharge device in general, a cathode is energized by a high voltage, resulting in electrons being field emitted from the cathode and accelerated across a vacuum gap to an anode, which typically has an opening through which a portion of the electron beam from the cathode moves. Those electrons in the beam which do not move through the opening strike the anode around the opening and flow through the anode to ground.
The focusing of the electron beam at the anode is accomplished primarily by the opening in the anode, and thus, the shape and quality of the beam depends to a large extent upon the size, configuration and other characteristics of the opening. However, there are inherent limitations on this technique with respect to the focusing and quality of the beam, since it is a passive focusing technique. It is often desirable that the electron beam have a better uniformity and a sharper focus than is possible through just the passive use of the anode opening.
Accordingly, it is a general object of the present invention to provide an electrode useful as an anode in an electron beam discharge device which corrects one or more of the disadvantages of the prior art noted above.
It is another object of the present invention to provide such an electrode which provides positive control over the focusing of the electron beam generated by an electron beam discharge device.
It is a further object of the present invention to provide such an electrode which uses a portion of the electron beam itself to provide the desired positive control.
It is an additional object of the present invention to provide such an electrode which provides a positive control which varies in strength in accordance with the energy level of the electron beam.
It is a still further object of the present invention to provide such an electrode which produces minimal adverse affects on the electron beam downstream of the electrode.
It is yet another object of the present invention to provide such an electrode which may be retrofitted to existing electron beam devices.